When a pair of conductors is applied with an electrical signal of a given signal frequency, conductors will transmit unequal parts of signal energy to conductors of an adjacent pair of conductors. The crosstalk phenomenon arises if the capacitive and inductive coupling between adjacent conductors is substantially higher than the couplings of the other conductor of the signal pair. Parameters that affect crosstalk includes the space between adjacent conducting wires, the dielectric constants among materials of conducting wire and the signal frequency of each signal pair.
The crosstalk phenomenon will be much more serious due to the small space among conducting wires in cables and jacks, which, especially for high speed transmission, will thereby cause the transmission quality to be unacceptable. Therefore, the Federal Communications Commission (FCC, U.S.) adopted guidelines about electrical connectors applied in telecommunication industry to provide intermateability
The primary reference, considered by many to be the international benchmark for commercially based telecommunication components and installations, is standard ANSI/EIA/TIA-568 (TIA-568) which is supplemented by TIA/EIA TSB40 (TSB40). Transmission parameters defined in TSB40 for an unshielded twisted pair (UTP) connector include attenuation, near-end crosstalk (NEXT) and return loss. Since crosstalk coupling is greatest between transmission segments close to the signal source, it is expressed in decibels as a frequency dependent value. The higher the NEXT loss magnitude, the better the crosstalk performance.
In the past, transmission requirements for Category 3 components are specified up to 16 MHz, while Category 4 components are specified up to 20 MHz. Nowadays, the requirements for Category 5 are specified up to 100 MHz. Though there are many types of commercially available pans that satisfy Category 5, they are still subjected to custom design and re-tooling. So, both The Siemon Company and Superior Modular Products, Inc. in the U.S. respectively designed common products which have already been patented under U.S. Pat. No. 5,295,869 and No. 5,299,956.